//     Backbone.js 1.4.0

//     (c) 2010-2019 Jeremy Ashkenas and DocumentCloud
//     Backbone may be freely distributed under the MIT license.
//     For all details and documentation:
//     http://backbonejs.org

(function(factory) {

	// Establish the root object, `window` (`self`) in the browser, or `global` on the server.
	// We use `self` instead of `window` for `WebWorker` support.
	var root = typeof self == 'object' && self.self === self && self ||
		typeof global == 'object' && global.global === global && global;

	// Set up Backbone appropriately for the environment. Start with AMD.
	if (typeof define === 'function' && define.amd) {
		define(['underscore', 'jquery', 'exports'], function(_, $, exports) {
			// Export global even in AMD case in case this script is loaded with
			// others that may still expect a global Backbone.
			root.Backbone = factory(root, exports, _, $);
		});

		// Next for Node.js or CommonJS. jQuery may not be needed as a module.
	} else if (typeof exports !== 'undefined') {
		var _ = require('underscore'), $;
		try { $ = require('jquery'); } catch (e) {}
		factory(root, exports, _, $);

		// Finally, as a browser global.
	} else {
		root.Backbone = factory(root, {}, root._, root.jQuery || root.Zepto || root.ender || root.$);
	}

})(function(root, Backbone, _, $) {

	// Initial Setup
	// -------------

	// Save the previous value of the `Backbone` variable, so that it can be
	// restored later on, if `noConflict` is used.
	var previousBackbone = root.Backbone;

	// Create a local reference to a common array method we'll want to use later.
	var slice = Array.prototype.slice;

	// Current version of the library. Keep in sync with `package.json`.
	Backbone.VERSION = '1.4.0';

	// For Backbone's purposes, jQuery, Zepto, Ender, or My Library (kidding) owns
	// the `$` variable.
	Backbone.$ = $;

	// Runs Backbone.js in *noConflict* mode, returning the `Backbone` variable
	// to its previous owner. Returns a reference to this Backbone object.
	Backbone.noConflict = function() {
		root.Backbone = previousBackbone;
		return this;
	};

	// Turn on `emulateHTTP` to support legacy HTTP servers. Setting this option
	// will fake `"PATCH"`, `"PUT"` and `"DELETE"` requests via the `_method` parameter and
	// set a `X-Http-Method-Override` header.
	Backbone.emulateHTTP = false;

	// Turn on `emulateJSON` to support legacy servers that can't deal with direct
	// `application/json` requests ... this will encode the body as
	// `application/x-www-form-urlencoded` instead and will send the model in a
	// form param named `model`.
	Backbone.emulateJSON = false;

	// Backbone.Events
	// ---------------

	// A module that can be mixed in to *any object* in order to provide it with
	// a custom event channel. You may bind a callback to an event with `on` or
	// remove with `off`; `trigger`-ing an event fires all callbacks in
	// succession.
	//
	//     var object = {};
	//     _.extend(object, Backbone.Events);
	//     object.on('expand', function(){ alert('expanded'); });
	//     object.trigger('expand');
	//
	var Events = Backbone.Events = {};

	// Regular expression used to split event strings.
	var eventSplitter = /\s+/;

	// A private global variable to share between listeners and listenees.
	var _listening;

	// Iterates over the standard `event, callback` (as well as the fancy multiple
	// space-separated events `"change blur", callback` and jQuery-style event
	// maps `{event: callback}`).
	var eventsApi = function(iteratee, events, name, callback, opts) {
		var i = 0, names;
		if (name && typeof name === 'object') {
			// Handle event maps.
			if (callback !== void 0 && 'context' in opts && opts.context === void 0) opts.context = callback;
			for (names = _.keys(name); i < names.length ; i++) {
				events = eventsApi(iteratee, events, names[i], name[names[i]], opts);
			}
		} else if (name && eventSplitter.test(name)) {
			// Handle space-separated event names by delegating them individually.
			for (names = name.split(eventSplitter); i < names.length; i++) {
				events = iteratee(events, names[i], callback, opts);
			}
		} else {
			// Finally, standard events.
			events = iteratee(events, name, callback, opts);
		}
		return events;
	};

	// Bind an event to a `callback` function. Passing `"all"` will bind
	// the callback to all events fired.
	Events.on = function(name, callback, context) {
		this._events = eventsApi(onApi, this._events || {}, name, callback, {
			context: context,
			ctx: this,
			listening: _listening
		});

		if (_listening) {
			var listeners = this._listeners || (this._listeners = {});
			listeners[_listening.id] = _listening;
			// Allow the listening to use a counter, instead of tracking
			// callbacks for library interop
			_listening.interop = false;
		}

		return this;
	};

	// Inversion-of-control versions of `on`. Tell *this* object to listen to
	// an event in another object... keeping track of what it's listening to
	// for easier unbinding later.
	Events.listenTo = function(obj, name, callback) {
		if (!obj) return this;
		var id = obj._listenId || (obj._listenId = _.uniqueId('l'));
		var listeningTo = this._listeningTo || (this._listeningTo = {});
		var listening = _listening = listeningTo[id];

		// This object is not listening to any other events on `obj` yet.
		// Setup the necessary references to track the listening callbacks.
		if (!listening) {
			this._listenId || (this._listenId = _.uniqueId('l'));
			listening = _listening = listeningTo[id] = new Listening(this, obj);
		}

		// Bind callbacks on obj.
		var error = tryCatchOn(obj, name, callback, this);
		_listening = void 0;

		if (error) throw error;
		// If the target obj is not Backbone.Events, track events manually.
		if (listening.interop) listening.on(name, callback);

		return this;
	};

	// The reducing API that adds a callback to the `events` object.
	var onApi = function(events, name, callback, options) {
		if (callback) {
			var handlers = events[name] || (events[name] = []);
			var context = options.context, ctx = options.ctx, listening = options.listening;
			if (listening) listening.count++;

			handlers.push({callback: callback, context: context, ctx: context || ctx, listening: listening});
		}
		return events;
	};

	// An try-catch guarded #on function, to prevent poisoning the global
	// `_listening` variable.
	var tryCatchOn = function(obj, name, callback, context) {
		try {
			obj.on(name, callback, context);
		} catch (e) {
			return e;
		}
	};

	// Remove one or many callbacks. If `context` is null, removes all
	// callbacks with that function. If `callback` is null, removes all
	// callbacks for the event. If `name` is null, removes all bound
	// callbacks for all events.
	Events.off = function(name, callback, context) {
		if (!this._events) return this;
		this._events = eventsApi(offApi, this._events, name, callback, {
			context: context,
			listeners: this._listeners
		});

		return this;
	};

	// Tell this object to stop listening to either specific events ... or
	// to every object it's currently listening to.
	Events.stopListening = function(obj, name, callback) {
		var listeningTo = this._listeningTo;
		if (!listeningTo) return this;

		var ids = obj ? [obj._listenId] : _.keys(listeningTo);
		for (var i = 0; i < ids.length; i++) {
			var listening = listeningTo[ids[i]];

			// If listening doesn't exist, this object is not currently
			// listening to obj. Break out early.
			if (!listening) break;

			listening.obj.off(name, callback, this);
			if (listening.interop) listening.off(name, callback);
		}
		if (_.isEmpty(listeningTo)) this._listeningTo = void 0;

		return this;
	};

	// The reducing API that removes a callback from the `events` object.
	var offApi = function(events, name, callback, options) {
		if (!events) return;

		var context = options.context, listeners = options.listeners;
		var i = 0, names;

		// Delete all event listeners and "drop" events.
		if (!name && !context && !callback) {
			for (names = _.keys(listeners); i < names.length; i++) {
				listeners[names[i]].cleanup();
			}
			return;
		}

		names = name ? [name] : _.keys(events);
		for (; i < names.length; i++) {
			name = names[i];
			var handlers = events[name];

			// Bail out if there are no events stored.
			if (!handlers) break;

			// Find any remaining events.
			var remaining = [];
			for (var j = 0; j < handlers.length; j++) {
				var handler = handlers[j];
				if (
					callback && callback !== handler.callback &&
					callback !== handler.callback._callback ||
					context && context !== handler.context
				) {
					remaining.push(handler);
				} else {
					var listening = handler.listening;
					if (listening) listening.off(name, callback);
				}
			}

			// Replace events if there are any remaining.  Otherwise, clean up.
			if (remaining.length) {
				events[name] = remaining;
			} else {
				delete events[name];
			}
		}

		return events;
	};

	// Bind an event to only be triggered a single time. After the first time
	// the callback is invoked, its listener will be removed. If multiple events
	// are passed in using the space-separated syntax, the handler will fire
	// once for each event, not once for a combination of all events.
	Events.once = function(name, callback, context) {
		// Map the event into a `{event: once}` object.
		var events = eventsApi(onceMap, {}, name, callback, this.off.bind(this));
		if (typeof name === 'string' && context == null) callback = void 0;
		return this.on(events, callback, context);
	};

	// Inversion-of-control versions of `once`.
	Events.listenToOnce = function(obj, name, callback) {
		// Map the event into a `{event: once}` object.
		var events = eventsApi(onceMap, {}, name, callback, this.stopListening.bind(this, obj));
		return this.listenTo(obj, events);
	};

	// Reduces the event callbacks into a map of `{event: onceWrapper}`.
	// `offer` unbinds the `onceWrapper` after it has been called.
	var onceMap = function(map, name, callback, offer) {
		if (callback) {
			var once = map[name] = _.once(function() {
				offer(name, once);
				callback.apply(this, arguments);
			});
			once._callback = callback;
		}
		return map;
	};

	// Trigger one or many events, firing all bound callbacks. Callbacks are
	// passed the same arguments as `trigger` is, apart from the event name
	// (unless you're listening on `"all"`, which will cause your callback to
	// receive the true name of the event as the first argument).
	Events.trigger = function(name) {
		if (!this._events) return this;

		var length = Math.max(0, arguments.length - 1);
		var args = Array(length);
		for (var i = 0; i < length; i++) args[i] = arguments[i + 1];

		eventsApi(triggerApi, this._events, name, void 0, args);
		return this;
	};

	// Handles triggering the appropriate event callbacks.
	var triggerApi = function(objEvents, name, callback, args) {
		if (objEvents) {
			var events = objEvents[name];
			var allEvents = objEvents.all;
			if (events && allEvents) allEvents = allEvents.slice();
			if (events) triggerEvents(events, args);
			if (allEvents) triggerEvents(allEvents, [name].concat(args));
		}
		return objEvents;
	};

	// A difficult-to-believe, but optimized internal dispatch function for
	// triggering events. Tries to keep the usual cases speedy (most internal
	// Backbone events have 3 arguments).
	var triggerEvents = function(events, args) {
		var ev, i = -1, l = events.length, a1 = args[0], a2 = args[1], a3 = args[2];
		switch (args.length) {
			case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx); return;
			case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1); return;
			case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2); return;
			case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, a1, a2, a3); return;
			default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args); return;
		}
	};

	// A listening class that tracks and cleans up memory bindings
	// when all callbacks have been offed.
	var Listening = function(listener, obj) {
		this.id = listener._listenId;
		this.listener = listener;
		this.obj = obj;
		this.interop = true;
		this.count = 0;
		this._events = void 0;
	};

	Listening.prototype.on = Events.on;

	// Offs a callback (or several).
	// Uses an optimized counter if the listenee uses Backbone.Events.
	// Otherwise, falls back to manual tracking to support events
	// library interop.
	Listening.prototype.off = function(name, callback) {
		var cleanup;
		if (this.interop) {
			this._events = eventsApi(offApi, this._events, name, callback, {
				context: void 0,
				listeners: void 0
			});
			cleanup = !this._events;
		} else {
			this.count--;
			cleanup = this.count === 0;
		}
		if (cleanup) this.cleanup();
	};

	// Cleans up memory bindings between the listener and the listenee.
	Listening.prototype.cleanup = function() {
		delete this.listener._listeningTo[this.obj._listenId];
		if (!this.interop) delete this.obj._listeners[this.id];
	};

	// Aliases for backwards compatibility.
	Events.bind   = Events.on;
	Events.unbind = Events.off;

	// Allow the `Backbone` object to serve as a global event bus, for folks who
	// want global "pubsub" in a convenient place.
	_.extend(Backbone, Events);

	// Backbone.Model
	// --------------

	// Backbone **Models** are the basic data object in the framework --
	// frequently representing a row in a table in a database on your server.
	// A discrete chunk of data and a bunch of useful, related methods for
	// performing computations and transformations on that data.

	// Create a new model with the specified attributes. A client id (`cid`)
	// is automatically generated and assigned for you.
	var Model = Backbone.Model = function(attributes, options) {
		var attrs = attributes || {};
		options || (options = {});
		this.preinitialize.apply(this, arguments);
		this.cid = _.uniqueId(this.cidPrefix);
		this.attributes = {};
		if (options.collection) this.collection = options.collection;
		if (options.parse) attrs = this.parse(attrs, options) || {};
		var defaults = _.result(this, 'defaults');
		attrs = _.defaults(_.extend({}, defaults, attrs), defaults);
		this.set(attrs, options);
		this.changed = {};
		this.initialize.apply(this, arguments);
	};

	// Attach all inheritable methods to the Model prototype.
	_.extend(Model.prototype, Events, {

		// A hash of attributes whose current and previous value differ.
		changed: null,

		// The value returned during the last failed validation.
		validationError: null,

		// The default name for the JSON `id` attribute is `"id"`. MongoDB and
		// CouchDB users may want to set this to `"_id"`.
		idAttribute: 'id',

		// The prefix is used to create the client id which is used to identify models locally.
		// You may want to override this if you're experiencing name clashes with model ids.
		cidPrefix: 'c',

		// preinitialize is an empty function by default. You can override it with a function
		// or object.  preinitialize will run before any instantiation logic is run in the Model.
		preinitialize: function(){},

		// Initialize is an empty function by default. Override it with your own
		// initialization logic.
		initialize: function(){},

		// Return a copy of the model's `attributes` object.
		toJSON: function(options) {
			return _.clone(this.attributes);
		},

		// Proxy `Backbone.sync` by default -- but override this if you need
		// custom syncing semantics for *this* particular model.
		sync: function() {
			return Backbone.sync.apply(this, arguments);
		},

		// Get the value of an attribute.
		get: function(attr) {
			return this.attributes[attr];
		},

		// Get the HTML-escaped value of an attribute.
		escape: function(attr) {
			return _.escape(this.get(attr));
		},

		// Returns `true` if the attribute contains a value that is not null
		// or undefined.
		has: function(attr) {
			return this.get(attr) != null;
		},

		// Special-cased proxy to underscore's `_.matches` method.
		matches: function(attrs) {
			return !!_.iteratee(attrs, this)(this.attributes);
		},

		// Set a hash of model attributes on the object, firing `"change"`. This is
		// the core primitive operation of a model, updating the data and notifying
		// anyone who needs to know about the change in state. The heart of the beast.
		set: function(key, val, options) {
			if (key == null) return this;

			// Handle both `"key", value` and `{key: value}` -style arguments.
			var attrs;
			if (typeof key === 'object') {
				attrs = key;
				options = val;
			} else {
				(attrs = {})[key] = val;
			}

			options || (options = {});

			// Run validation.
			if (!this._validate(attrs, options)) return false;

			// Extract attributes and options.
			var unset      = options.unset;
			var silent     = options.silent;
			var changes    = [];
			var changing   = this._changing;
			this._changing = true;

			if (!changing) {
				this._previousAttributes = _.clone(this.attributes);
				this.changed = {};
			}

			var current = this.attributes;
			var changed = this.changed;
			var prev    = this._previousAttributes;

			// For each `set` attribute, update or delete the current value.
			for (var attr in attrs) {
				val = attrs[attr];
				if (!_.isEqual(current[attr], val)) changes.push(attr);
				if (!_.isEqual(prev[attr], val)) {
					changed[attr] = val;
				} else {
					delete changed[attr];
				}
				unset ? delete current[attr] : current[attr] = val;
			}

			// Update the `id`.
			if (this.idAttribute in attrs) this.id = this.get(this.idAttribute);

			// Trigger all relevant attribute changes.
			if (!silent) {
				if (changes.length) this._pending = options;
				for (var i = 0; i < changes.length; i++) {
					this.trigger('change:' + changes[i], this, current[changes[i]], options);
				}
			}

			// You might be wondering why there's a `while` loop here. Changes can
			// be recursively nested within `"change"` events.
			if (changing) return this;
			if (!silent) {
				while (this._pending) {
					options = this._pending;
					this._pending = false;
					this.trigger('change', this, options);
				}
			}
			this._pending = false;
			this._changing = false;
			return this;
		},

		// Remove an attribute from the model, firing `"change"`. `unset` is a noop
		// if the attribute doesn't exist.
		unset: function(attr, options) {
			return this.set(attr, void 0, _.extend({}, options, {unset: true}));
		},

		// Clear all attributes on the model, firing `"change"`.
		clear: function(options) {
			var attrs = {};
			for (var key in this.attributes) attrs[key] = void 0;
			return this.set(attrs, _.extend({}, options, {unset: true}));
		},

		// Determine if the model has changed since the last `"change"` event.
		// If you specify an attribute name, determine if that attribute has changed.
		hasChanged: function(attr) {
			if (attr == null) return !_.isEmpty(this.changed);
			return _.has(this.changed, attr);
		},

		// Return an object containing all the attributes that have changed, or
		// false if there are no changed attributes. Useful for determining what
		// parts of a view need to be updated and/or what attributes need to be
		// persisted to the server. Unset attributes will be set to undefined.
		// You can also pass an attributes object to diff against the model,
		// determining if there *would be* a change.
		changedAttributes: function(diff) {
			if (!diff) return this.hasChanged() ? _.clone(this.changed) : false;
			var old = this._changing ? this._previousAttributes : this.attributes;
			var changed = {};
			var hasChanged;
			for (var attr in diff) {
				var val = diff[attr];
				if (_.isEqual(old[attr], val)) continue;
				changed[attr] = val;
				hasChanged = true;
			}
			return hasChanged ? changed : false;
		},

		// Get the previous value of an attribute, recorded at the time the last
		// `"change"` event was fired.
		previous: function(attr) {
			if (attr == null || !this._previousAttributes) return null;
			return this._previousAttributes[attr];
		},

		// Get all of the attributes of the model at the time of the previous
		// `"change"` event.
		previousAttributes: function() {
			return _.clone(this._previousAttributes);
		},

		// Fetch the model from the server, merging the response with the model's
		// local attributes. Any changed attributes will trigger a "change" event.
		fetch: function(options) {
			options = _.extend({parse: true}, options);
			var model = this;
			var success = options.success;
			options.success = function(resp) {
				var serverAttrs = options.parse ? model.parse(resp, options) : resp;
				if (!model.set(serverAttrs, options)) return false;
				if (success) success.call(options.context, model, resp, options);
				model.trigger('sync', model, resp, options);
			};
			wrapError(this, options);
			return this.sync('read', this, options);
		},

		// Set a hash of model attributes, and sync the model to the server.
		// If the server returns an attributes hash that differs, the model's
		// state will be `set` again.
		save: function(key, val, options) {
			// Handle both `"key", value` and `{key: value}` -style arguments.
			var attrs;
			if (key == null || typeof key === 'object') {
				attrs = key;
				options = val;
			} else {
				(attrs = {})[key] = val;
			}

			options = _.extend({validate: true, parse: true}, options);
			var wait = options.wait;

			// If we're not waiting and attributes exist, save acts as
			// `set(attr).save(null, opts)` with validation. Otherwise, check if
			// the model will be valid when the attributes, if any, are set.
			if (attrs && !wait) {
				if (!this.set(attrs, options)) return false;
			} else if (!this._validate(attrs, options)) {
				return false;
			}

			// After a successful server-side save, the client is (optionally)
			// updated with the server-side state.
			var model = this;
			var success = options.success;
			var attributes = this.attributes;
			options.success = function(resp) {
				// Ensure attributes are restored during synchronous saves.
				model.attributes = attributes;
				var serverAttrs = options.parse ? model.parse(resp, options) : resp;
				if (wait) serverAttrs = _.extend({}, attrs, serverAttrs);
				if (serverAttrs && !model.set(serverAttrs, options)) return false;
				if (success) success.call(options.context, model, resp, options);
				model.trigger('sync', model, resp, options);
			};
			wrapError(this, options);

			// Set temporary attributes if `{wait: true}` to properly find new ids.
			if (attrs && wait) this.attributes = _.extend({}, attributes, attrs);

			var method = this.isNew() ? 'create' : options.patch ? 'patch' : 'update';
			if (method === 'patch' && !options.attrs) options.attrs = attrs;
			var xhr = this.sync(method, this, options);

			// Restore attributes.
			this.attributes = attributes;

			return xhr;
		},

		// Destroy this model on the server if it was already persisted.
		// Optimistically removes the model from its collection, if it has one.
		// If `wait: true` is passed, waits for the server to respond before removal.
		destroy: function(options) {
			options = options ? _.clone(options) : {};
			var model = this;
			var success = options.success;
			var wait = options.wait;

			var destroy = function() {
				model.stopListening();
				model.trigger('destroy', model, model.collection, options);
			};

			options.success = function(resp) {
				if (wait) destroy();
				if (success) success.call(options.context, model, resp, options);
				if (!model.isNew()) model.trigger('sync', model, resp, options);
			};

			var xhr = false;
			if (this.isNew()) {
				_.defer(options.success);
			} else {
				wrapError(this, options);
				xhr = this.sync('delete', this, options);
			}
			if (!wait) destroy();
			return xhr;
		},

		// Default URL for the model's representation on the server -- if you're
		// using Backbone's restful methods, override this to change the endpoint
		// that will be called.
		url: function() {
			var base =
				_.result(this, 'urlRoot') ||
				_.result(this.collection, 'url') ||
				urlError();
			if (this.isNew()) return base;
			var id = this.get(this.idAttribute);
			return base.replace(/[^\/]$/, '$&/') + encodeURIComponent(id);
		},

		// **parse** converts a response into the hash of attributes to be `set` on
		// the model. The default implementation is just to pass the response along.
		parse: function(resp, options) {
			return resp;
		},

		// Create a new model with identical attributes to this one.
		clone: function() {
			return new this.constructor(this.attributes);
		},

		// A model is new if it has never been saved to the server, and lacks an id.
		isNew: function() {
			return !this.has(this.idAttribute);
		},

		// Check if the model is currently in a valid state.
		isValid: function(options) {
			return this._validate({}, _.extend({}, options, {validate: true}));
		},

		// Run validation against the next complete set of model attributes,
		// returning `true` if all is well. Otherwise, fire an `"invalid"` event.
		_validate: function(attrs, options) {
			if (!options.validate || !this.validate) return true;
			attrs = _.extend({}, this.attributes, attrs);
			var error = this.validationError = this.validate(attrs, options) || null;
			if (!error) return true;
			this.trigger('invalid', this, error, _.extend(options, {validationError: error}));
			return false;
		}

	});

	// Backbone.Collection
	// -------------------

	// If models tend to represent a single row of data, a Backbone Collection is
	// more analogous to a table full of data ... or a small slice or page of that
	// table, or a collection of rows that belong together for a particular reason
	// -- all of the messages in this particular folder, all of the documents
	// belonging to this particular author, and so on. Collections maintain
	// indexes of their models, both in order, and for lookup by `id`.

	// Create a new **Collection**, perhaps to contain a specific type of `model`.
	// If a `comparator` is specified, the Collection will maintain
	// its models in sort order, as they're added and removed.
	var Collection = Backbone.Collection = function(models, options) {
		options || (options = {});
		this.preinitialize.apply(this, arguments);
		if (options.model) this.model = options.model;
		if (options.comparator !== void 0) this.comparator = options.comparator;
		this._reset();
		this.initialize.apply(this, arguments);
		if (models) this.reset(models, _.extend({silent: true}, options));
	};

	// Default options for `Collection#set`.
	var setOptions = {add: true, remove: true, merge: true};
	var addOptions = {add: true, remove: false};

	// Splices `insert` into `array` at index `at`.
	var splice = function(array, insert, at) {
		at = Math.min(Math.max(at, 0), array.length);
		var tail = Array(array.length - at);
		var length = insert.length;
		var i;
		for (i = 0; i < tail.length; i++) tail[i] = array[i + at];
		for (i = 0; i < length; i++) array[i + at] = insert[i];
		for (i = 0; i < tail.length; i++) array[i + length + at] = tail[i];
	};

	// Define the Collection's inheritable methods.
	_.extend(Collection.prototype, Events, {

		// The default model for a collection is just a **Backbone.Model**.
		// This should be overridden in most cases.
		model: Model,


		// preinitialize is an empty function by default. You can override it with a function
		// or object.  preinitialize will run before any instantiation logic is run in the Collection.
		preinitialize: function(){},

		// Initialize is an empty function by default. Override it with your own
		// initialization logic.
		initialize: function(){},

		// The JSON representation of a Collection is an array of the
		// models' attributes.
		toJSON: function(options) {
			return this.map(function(model) { return model.toJSON(options); });
		},

		// Proxy `Backbone.sync` by default.
		sync: function() {
			return Backbone.sync.apply(this, arguments);
		},

		// Add a model, or list of models to the set. `models` may be Backbone
		// Models or raw JavaScript objects to be converted to Models, or any
		// combination of the two.
		add: function(models, options) {
			return this.set(models, _.extend({merge: false}, options, addOptions));
		},

		// Remove a model, or a list of models from the set.
		remove: function(models, options) {
			options = _.extend({}, options);
			var singular = !_.isArray(models);
			models = singular ? [models] : models.slice();
			var removed = this._removeModels(models, options);
			if (!options.silent && removed.length) {
				options.changes = {added: [], merged: [], removed: removed};
				this.trigger('update', this, options);
			}
			return singular ? removed[0] : removed;
		},

		// Update a collection by `set`-ing a new list of models, adding new ones,
		// removing models that are no longer present, and merging models that
		// already exist in the collection, as necessary. Similar to **Model#set**,
		// the core operation for updating the data contained by the collection.
		set: function(models, options) {
			if (models == null) return;

			options = _.extend({}, setOptions, options);
			if (options.parse && !this._isModel(models)) {
				models = this.parse(models, options) || [];
			}

			var singular = !_.isArray(models);
			models = singular ? [models] : models.slice();

			var at = options.at;
			if (at != null) at = +at;
			if (at > this.length) at = this.length;
			if (at < 0) at += this.length + 1;

			var set = [];
			var toAdd = [];
			var toMerge = [];
			var toRemove = [];
			var modelMap = {};

			var add = options.add;
			var merge = options.merge;
			var remove = options.remove;

			var sort = false;
			var sortable = this.comparator && at == null && options.sort !== false;
			var sortAttr = _.isString(this.comparator) ? this.comparator : null;

			// Turn bare objects into model references, and prevent invalid models
			// from being added.
			var model, i;
			for (i = 0; i < models.length; i++) {
				model = models[i];

				// If a duplicate is found, prevent it from being added and
				// optionally merge it into the existing model.
				var existing = this.get(model);
				if (existing) {
					if (merge && model !== existing) {
						var attrs = this._isModel(model) ? model.attributes : model;
						if (options.parse) attrs = existing.parse(attrs, options);
						existing.set(attrs, options);
						toMerge.push(existing);
						if (sortable && !sort) sort = existing.hasChanged(sortAttr);
					}
					if (!modelMap[existing.cid]) {
						modelMap[existing.cid] = true;
						set.push(existing);
					}
					models[i] = existing;

					// If this is a new, valid model, push it to the `toAdd` list.
				} else if (add) {
					model = models[i] = this._prepareModel(model, options);
					if (model) {
						toAdd.push(model);
						this._addReference(model, options);
						modelMap[model.cid] = true;
						set.push(model);
					}
				}
			}

			// Remove stale models.
			if (remove) {
				for (i = 0; i < this.length; i++) {
					model = this.models[i];
					if (!modelMap[model.cid]) toRemove.push(model);
				}
				if (toRemove.length) this._removeModels(toRemove, options);
			}

			// See if sorting is needed, update `length` and splice in new models.
			var orderChanged = false;
			var replace = !sortable && add && remove;
			if (set.length && replace) {
				orderChanged = this.length !== set.length || _.some(this.models, function(m, index) {
					return m !== set[index];
				});
				this.models.length = 0;
				splice(this.models, set, 0);
				this.length = this.models.length;
			} else if (toAdd.length) {
				if (sortable) sort = true;
				splice(this.models, toAdd, at == null ? this.length : at);
				this.length = this.models.length;
			}

			// Silently sort the collection if appropriate.
			if (sort) this.sort({silent: true});

			// Unless silenced, it's time to fire all appropriate add/sort/update events.
			if (!options.silent) {
				for (i = 0; i < toAdd.length; i++) {
					if (at != null) options.index = at + i;
					model = toAdd[i];
					model.trigger('add', model, this, options);
				}
				if (sort || orderChanged) this.trigger('sort', this, options);
				if (toAdd.length || toRemove.length || toMerge.length) {
					options.changes = {
						added: toAdd,
						removed: toRemove,
						merged: toMerge
					};
					this.trigger('update', this, options);
				}
			}

			// Return the added (or merged) model (or models).
			return singular ? models[0] : models;
		},

		// When you have more items than you want to add or remove individually,
		// you can reset the entire set with a new list of models, without firing
		// any granular `add` or `remove` events. Fires `reset` when finished.
		// Useful for bulk operations and optimizations.
		reset: function(models, options) {
			options = options ? _.clone(options) : {};
			for (var i = 0; i < this.models.length; i++) {
				this._removeReference(this.models[i], options);
			}
			options.previousModels = this.models;
			this._reset();
			models = this.add(models, _.extend({silent: true}, options));
			if (!options.silent) this.trigger('reset', this, options);
			return models;
		},

		// Add a model to the end of the collection.
		push: function(model, options) {
			return this.add(model, _.extend({at: this.length}, options));
		},

		// Remove a model from the end of the collection.
		pop: function(options) {
			var model = this.at(this.length - 1);
			return this.remove(model, options);
		},

		// Add a model to the beginning of the collection.
		unshift: function(model, options) {
			return this.add(model, _.extend({at: 0}, options));
		},

		// Remove a model from the beginning of the collection.
		shift: function(options) {
			var model = this.at(0);
			return this.remove(model, options);
		},

		// Slice out a sub-array of models from the collection.
		slice: function() {
			return slice.apply(this.models, arguments);
		},

		// Get a model from the set by id, cid, model object with id or cid
		// properties, or an attributes object that is transformed through modelId.
		get: function(obj) {
			if (obj == null) return void 0;
			return this._byId[obj] ||
				this._byId[this.modelId(this._isModel(obj) ? obj.attributes : obj)] ||
				obj.cid && this._byId[obj.cid];
		},

		// Returns `true` if the model is in the collection.
		has: function(obj) {
			return this.get(obj) != null;
		},

		// Get the model at the given index.
		at: function(index) {
			if (index < 0) index += this.length;
			return this.models[index];
		},

		// Return models with matching attributes. Useful for simple cases of
		// `filter`.
		where: function(attrs, first) {
			return this[first ? 'find' : 'filter'](attrs);
		},

		// Return the first model with matching attributes. Useful for simple cases
		// of `find`.
		findWhere: function(attrs) {
			return this.where(attrs, true);
		},

		// Force the collection to re-sort itself. You don't need to call this under
		// normal circumstances, as the set will maintain sort order as each item
		// is added.
		sort: function(options) {
			var comparator = this.comparator;
			if (!comparator) throw new Error('Cannot sort a set without a comparator');
			options || (options = {});

			var length = comparator.length;
			if (_.isFunction(comparator)) comparator = comparator.bind(this);

			// Run sort based on type of `comparator`.
			if (length === 1 || _.isString(comparator)) {
				this.models = this.sortBy(comparator);
			} else {
				this.models.sort(comparator);
			}
			if (!options.silent) this.trigger('sort', this, options);
			return this;
		},

		// Pluck an attribute from each model in the collection.
		pluck: function(attr) {
			return this.map(attr + '');
		},

		// Fetch the default set of models for this collection, resetting the
		// collection when they arrive. If `reset: true` is passed, the response
		// data will be passed through the `reset` method instead of `set`.
		fetch: function(options) {
			options = _.extend({parse: true}, options);
			var success = options.success;
			var collection = this;
			options.success = function(resp) {
				var method = options.reset ? 'reset' : 'set';
				collection[method](resp, options);
				if (success) success.call(options.context, collection, resp, options);
				collection.trigger('sync', collection, resp, options);
			};
			wrapError(this, options);
			return this.sync('read', this, options);
		},

		// Create a new instance of a model in this collection. Add the model to the
		// collection immediately, unless `wait: true` is passed, in which case we
		// wait for the server to agree.
		create: function(model, options) {
			options = options ? _.clone(options) : {};
			var wait = options.wait;
			model = this._prepareModel(model, options);
			if (!model) return false;
			if (!wait) this.add(model, options);
			var collection = this;
			var success = options.success;
			options.success = function(m, resp, callbackOpts) {
				if (wait) collection.add(m, callbackOpts);
				if (success) success.call(callbackOpts.context, m, resp, callbackOpts);
			};
			model.save(null, options);
			return model;
		},

		// **parse** converts a response into a list of models to be added to the
		// collection. The default implementation is just to pass it through.
		parse: function(resp, options) {
			return resp;
		},

		// Create a new collection with an identical list of models as this one.
		clone: function() {
			return new this.constructor(this.models, {
				model: this.model,
				comparator: this.comparator
			});
		},

		// Define how to uniquely identify models in the collection.
		modelId: function(attrs) {
			return attrs[this.model.prototype.idAttribute || 'id'];
		},

		// Get an iterator of all models in this collection.
		values: function() {
			return new CollectionIterator(this, ITERATOR_VALUES);
		},

		// Get an iterator of all model IDs in this collection.
		keys: function() {
			return new CollectionIterator(this, ITERATOR_KEYS);
		},

		// Get an iterator of all [ID, model] tuples in this collection.
		entries: function() {
			return new CollectionIterator(this, ITERATOR_KEYSVALUES);
		},

		// Private method to reset all internal state. Called when the collection
		// is first initialized or reset.
		_reset: function() {
			this.length = 0;
			this.models = [];
			this._byId  = {};
		},

		// Prepare a hash of attributes (or other model) to be added to this
		// collection.
		_prepareModel: function(attrs, options) {
			if (this._isModel(attrs)) {
				if (!attrs.collection) attrs.collection = this;
				return attrs;
			}
			options = options ? _.clone(options) : {};
			options.collection = this;
			var model = new this.model(attrs, options);
			if (!model.validationError) return model;
			this.trigger('invalid', this, model.validationError, options);
			return false;
		},

		// Internal method called by both remove and set.
		_removeModels: function(models, options) {
			var removed = [];
			for (var i = 0; i < models.length; i++) {
				var model = this.get(models[i]);
				if (!model) continue;

				var index = this.indexOf(model);
				this.models.splice(index, 1);
				this.length--;

				// Remove references before triggering 'remove' event to prevent an
				// infinite loop. #3693
				delete this._byId[model.cid];
				var id = this.modelId(model.attributes);
				if (id != null) delete this._byId[id];

				if (!options.silent) {
					options.index = index;
					model.trigger('remove', model, this, options);
				}

				removed.push(model);
				this._removeReference(model, options);
			}
			return removed;
		},

		// Method for checking whether an object should be considered a model for
		// the purposes of adding to the collection.
		_isModel: function(model) {
			return model instanceof Model;
		},

		// Internal method to create a model's ties to a collection.
		_addReference: function(model, options) {
			this._byId[model.cid] = model;
			var id = this.modelId(model.attributes);
			if (id != null) this._byId[id] = model;
			model.on('all', this._onModelEvent, this);
		},

		// Internal method to sever a model's ties to a collection.
		_removeReference: function(model, options) {
			delete this._byId[model.cid];
			var id = this.modelId(model.attributes);
			if (id != null) delete this._byId[id];
			if (this === model.collection) delete model.collection;
			model.off('all', this._onModelEvent, this);
		},

		// Internal method called every time a model in the set fires an event.
		// Sets need to update their indexes when models change ids. All other
		// events simply proxy through. "add" and "remove" events that originate
		// in other collections are ignored.
		_onModelEvent: function(event, model, collection, options) {
			if (model) {
				if ((event === 'add' || event === 'remove') && collection !== this) return;
				if (event === 'destroy') this.remove(model, options);
				if (event === 'change') {
					var prevId = this.modelId(model.previousAttributes());
					var id = this.modelId(model.attributes);
					if (prevId !== id) {
						if (prevId != null) delete this._byId[prevId];
						if (id != null) this._byId[id] = model;
					}
				}
			}
			this.trigger.apply(this, arguments);
		}

	});

	// Defining an @@iterator method implements JavaScript's Iterable protocol.
	// In modern ES2015 browsers, this value is found at Symbol.iterator.
	/* global Symbol */
	var $$iterator = typeof Symbol === 'function' && Symbol.iterator;
	if ($$iterator) {
		Collection.prototype[$$iterator] = Collection.prototype.values;
	}

	// CollectionIterator
	// ------------------

	// A CollectionIterator implements JavaScript's Iterator protocol, allowing the
	// use of `for of` loops in modern browsers and interoperation between
	// Backbone.Collection and other JavaScript functions and third-party libraries
	// which can operate on Iterables.
	var CollectionIterator = function(collection, kind) {
		this._collection = collection;
		this._kind = kind;
		this._index = 0;
	};

	// This "enum" defines the three possible kinds of values which can be emitted
	// by a CollectionIterator that correspond to the values(), keys() and entries()
	// methods on Collection, respectively.
	var ITERATOR_VALUES = 1;
	var ITERATOR_KEYS = 2;
	var ITERATOR_KEYSVALUES = 3;

	// All Iterators should themselves be Iterable.
	if ($$iterator) {
		CollectionIterator.prototype[$$iterator] = function() {
			return this;
		};
	}

	CollectionIterator.prototype.next = function() {
		if (this._collection) {

			// Only continue iterating if the iterated collection is long enough.
			if (this._index < this._collection.length) {
				var model = this._collection.at(this._index);
				this._index++;

				// Construct a value depending on what kind of values should be iterated.
				var value;
				if (this._kind === ITERATOR_VALUES) {
					value = model;
				} else {
					var id = this._collection.modelId(model.attributes);
					if (this._kind === ITERATOR_KEYS) {
						value = id;
					} else { // ITERATOR_KEYSVALUES
						value = [id, model];
					}
				}
				return {value: value, done: false};
			}

			// Once exhausted, remove the reference to the collection so future
			// calls to the next method always return done.
			this._collection = void 0;
		}

		return {value: void 0, done: true};
	};

	// Backbone.View
	// -------------

	// Backbone Views are almost more convention than they are actual code. A View
	// is simply a JavaScript object that represents a logical chunk of UI in the
	// DOM. This might be a single item, an entire list, a sidebar or panel, or
	// even the surrounding frame which wraps your whole app. Defining a chunk of
	// UI as a **View** allows you to define your DOM events declaratively, without
	// having to worry about render order ... and makes it easy for the view to
	// react to specific changes in the state of your models.

	// Creating a Backbone.View creates its initial element outside of the DOM,
	// if an existing element is not provided...
	var View = Backbone.View = function(options) {
		this.cid = _.uniqueId('view');
		this.preinitialize.apply(this, arguments);
		_.extend(this, _.pick(options, viewOptions));
		this._ensureElement();
		this.initialize.apply(this, arguments);
	};

	// Cached regex to split keys for `delegate`.
	var delegateEventSplitter = /^(\S+)\s*(.*)$/;

	// List of view options to be set as properties.
	var viewOptions = ['model', 'collection', 'el', 'id', 'attributes', 'className', 'tagName', 'events'];

	// Set up all inheritable **Backbone.View** properties and methods.
	_.extend(View.prototype, Events, {

		// The default `tagName` of a View's element is `"div"`.
		tagName: 'div',

		// jQuery delegate for element lookup, scoped to DOM elements within the
		// current view. This should be preferred to global lookups where possible.
		$: function(selector) {
			return this.$el.find(selector);
		},

		// preinitialize is an empty function by default. You can override it with a function
		// or object.  preinitialize will run before any instantiation logic is run in the View
		preinitialize: function(){},

		// Initialize is an empty function by default. Override it with your own
		// initialization logic.
		initialize: function(){},

		// **render** is the core function that your view should override, in order
		// to populate its element (`this.el`), with the appropriate HTML. The
		// convention is for **render** to always return `this`.
		render: function() {
			return this;
		},

		// Remove this view by taking the element out of the DOM, and removing any
		// applicable Backbone.Events listeners.
		remove: function() {
			this._removeElement();
			this.stopListening();
			return this;
		},

		// Remove this view's element from the document and all event listeners
		// attached to it. Exposed for subclasses using an alternative DOM
		// manipulation API.
		_removeElement: function() {
			this.$el.remove();
		},

		// Change the view's element (`this.el` property) and re-delegate the
		// view's events on the new element.
		setElement: function(element) {
			this.undelegateEvents();
			this._setElement(element);
			this.delegateEvents();
			return this;
		},

		// Creates the `this.el` and `this.$el` references for this view using the
		// given `el`. `el` can be a CSS selector or an HTML string, a jQuery
		// context or an element. Subclasses can override this to utilize an
		// alternative DOM manipulation API and are only required to set the
		// `this.el` property.
		_setElement: function(el) {
			this.$el = el instanceof Backbone.$ ? el : Backbone.$(el);
			this.el = this.$el[0];
		},

		// Set callbacks, where `this.events` is a hash of
		//
		// *{"event selector": "callback"}*
		//
		//     {
		//       'mousedown .title':  'edit',
		//       'click .button':     'save',
		//       'click .open':       function(e) { ... }
		//     }
		//
		// pairs. Callbacks will be bound to the view, with `this` set properly.
		// Uses event delegation for efficiency.
		// Omitting the selector binds the event to `this.el`.
		delegateEvents: function(events) {
			events || (events = _.result(this, 'events'));
			if (!events) return this;
			this.undelegateEvents();
			for (var key in events) {
				var method = events[key];
				if (!_.isFunction(method)) method = this[method];
				if (!method) continue;
				var match = key.match(delegateEventSplitter);
				this.delegate(match[1], match[2], method.bind(this));
			}
			return this;
		},

		// Add a single event listener to the view's element (or a child element
		// using `selector`). This only works for delegate-able events: not `focus`,
		// `blur`, and not `change`, `submit`, and `reset` in Internet Explorer.
		delegate: function(eventName, selector, listener) {
			this.$el.on(eventName + '.delegateEvents' + this.cid, selector, listener);
			return this;
		},

		// Clears all callbacks previously bound to the view by `delegateEvents`.
		// You usually don't need to use this, but may wish to if you have multiple
		// Backbone views attached to the same DOM element.
		undelegateEvents: function() {
			if (this.$el) this.$el.off('.delegateEvents' + this.cid);
			return this;
		},

		// A finer-grained `undelegateEvents` for removing a single delegated event.
		// `selector` and `listener` are both optional.
		undelegate: function(eventName, selector, listener) {
			this.$el.off(eventName + '.delegateEvents' + this.cid, selector, listener);
			return this;
		},

		// Produces a DOM element to be assigned to your view. Exposed for
		// subclasses using an alternative DOM manipulation API.
		_createElement: function(tagName) {
			return document.createElement(tagName);
		},

		// Ensure that the View has a DOM element to render into.
		// If `this.el` is a string, pass it through `$()`, take the first
		// matching element, and re-assign it to `el`. Otherwise, create
		// an element from the `id`, `className` and `tagName` properties.
		_ensureElement: function() {
			if (!this.el) {
				var attrs = _.extend({}, _.result(this, 'attributes'));
				if (this.id) attrs.id = _.result(this, 'id');
				if (this.className) attrs['class'] = _.result(this, 'className');
				this.setElement(this._createElement(_.result(this, 'tagName')));
				this._setAttributes(attrs);
			} else {
				this.setElement(_.result(this, 'el'));
			}
		},

		// Set attributes from a hash on this view's element.  Exposed for
		// subclasses using an alternative DOM manipulation API.
		_setAttributes: function(attributes) {
			this.$el.attr(attributes);
		}

	});

	// Proxy Backbone class methods to Underscore functions, wrapping the model's
	// `attributes` object or collection's `models` array behind the scenes.
	//
	// collection.filter(function(model) { return model.get('age') > 10 });
	// collection.each(this.addView);
	//
	// `Function#apply` can be slow so we use the method's arg count, if we know it.
	var addMethod = function(base, length, method, attribute) {
		switch (length) {
			case 1: return function() {
				return base[method](this[attribute]);
			};
			case 2: return function(value) {
				return base[method](this[attribute], value);
			};
			case 3: return function(iteratee, context) {
				return base[method](this[attribute], cb(iteratee, this), context);
			};
			case 4: return function(iteratee, defaultVal, context) {
				return base[method](this[attribute], cb(iteratee, this), defaultVal, context);
			};
			default: return function() {
				var args = slice.call(arguments);
				args.unshift(this[attribute]);
				return base[method].apply(base, args);
			};
		}
	};

	var addUnderscoreMethods = function(Class, base, methods, attribute) {
		_.each(methods, function(length, method) {
			if (base[method]) Class.prototype[method] = addMethod(base, length, method, attribute);
		});
	};

	// Support `collection.sortBy('attr')` and `collection.findWhere({id: 1})`.
	var cb = function(iteratee, instance) {
		if (_.isFunction(iteratee)) return iteratee;
		if (_.isObject(iteratee) && !instance._isModel(iteratee)) return modelMatcher(iteratee);
		if (_.isString(iteratee)) return function(model) { return model.get(iteratee); };
		return iteratee;
	};
	var modelMatcher = function(attrs) {
		var matcher = _.matches(attrs);
		return function(model) {
			return matcher(model.attributes);
		};
	};

	// Underscore methods that we want to implement on the Collection.
	// 90% of the core usefulness of Backbone Collections is actually implemented
	// right here:
	var collectionMethods = {forEach: 3, each: 3, map: 3, collect: 3, reduce: 0,
		foldl: 0, inject: 0, reduceRight: 0, foldr: 0, find: 3, detect: 3, filter: 3,
		select: 3, reject: 3, every: 3, all: 3, some: 3, any: 3, include: 3, includes: 3,
		contains: 3, invoke: 0, max: 3, min: 3, toArray: 1, size: 1, first: 3,
		head: 3, take: 3, initial: 3, rest: 3, tail: 3, drop: 3, last: 3,
		without: 0, difference: 0, indexOf: 3, shuffle: 1, lastIndexOf: 3,
		isEmpty: 1, chain: 1, sample: 3, partition: 3, groupBy: 3, countBy: 3,
		sortBy: 3, indexBy: 3, findIndex: 3, findLastIndex: 3};


	// Underscore methods that we want to implement on the Model, mapped to the
	// number of arguments they take.
	var modelMethods = {keys: 1, values: 1, pairs: 1, invert: 1, pick: 0,
		omit: 0, chain: 1, isEmpty: 1};

	// Mix in each Underscore method as a proxy to `Collection#models`.

	_.each([
		[Collection, collectionMethods, 'models'],
		[Model, modelMethods, 'attributes']
	], function(config) {
		var Base = config[0],
			methods = config[1],
			attribute = config[2];

		Base.mixin = function(obj) {
			var mappings = _.reduce(_.functions(obj), function(memo, name) {
				memo[name] = 0;
				return memo;
			}, {});
			addUnderscoreMethods(Base, obj, mappings, attribute);
		};

		addUnderscoreMethods(Base, _, methods, attribute);
	});

	// Backbone.sync
	// -------------

	// Override this function to change the manner in which Backbone persists
	// models to the server. You will be passed the type of request, and the
	// model in question. By default, makes a RESTful Ajax request
	// to the model's `url()`. Some possible customizations could be:
	//
	// * Use `setTimeout` to batch rapid-fire updates into a single request.
	// * Send up the models as XML instead of JSON.
	// * Persist models via WebSockets instead of Ajax.
	//
	// Turn on `Backbone.emulateHTTP` in order to send `PUT` and `DELETE` requests
	// as `POST`, with a `_method` parameter containing the true HTTP method,
	// as well as all requests with the body as `application/x-www-form-urlencoded`
	// instead of `application/json` with the model in a param named `model`.
	// Useful when interfacing with server-side languages like **PHP** that make
	// it difficult to read the body of `PUT` requests.
	Backbone.sync = function(method, model, options) {
		var type = methodMap[method];

		// Default options, unless specified.
		_.defaults(options || (options = {}), {
			emulateHTTP: Backbone.emulateHTTP,
			emulateJSON: Backbone.emulateJSON
		});

		// Default JSON-request options.
		var params = {type: type, dataType: 'json'};

		// Ensure that we have a URL.
		if (!options.url) {
			params.url = _.result(model, 'url') || urlError();
		}

		// Ensure that we have the appropriate request data.
		if (options.data == null && model && (method === 'create' || method === 'update' || method === 'patch')) {
			params.contentType = 'application/json';
			params.data = JSON.stringify(options.attrs || model.toJSON(options));
		}

		// For older servers, emulate JSON by encoding the request into an HTML-form.
		if (options.emulateJSON) {
			params.contentType = 'application/x-www-form-urlencoded';
			params.data = params.data ? {model: params.data} : {};
		}

		// For older servers, emulate HTTP by mimicking the HTTP method with `_method`
		// And an `X-HTTP-Method-Override` header.
		if (options.emulateHTTP && (type === 'PUT' || type === 'DELETE' || type === 'PATCH')) {
			params.type = 'POST';
			if (options.emulateJSON) params.data._method = type;
			var beforeSend = options.beforeSend;
			options.beforeSend = function(xhr) {
				xhr.setRequestHeader('X-HTTP-Method-Override', type);
				if (beforeSend) return beforeSend.apply(this, arguments);
			};
		}

		// Don't process data on a non-GET request.
		if (params.type !== 'GET' && !options.emulateJSON) {
			params.processData = false;
		}

		// Pass along `textStatus` and `errorThrown` from jQuery.
		var error = options.error;
		options.error = function(xhr, textStatus, errorThrown) {
			options.textStatus = textStatus;
			options.errorThrown = errorThrown;
			if (error) error.call(options.context, xhr, textStatus, errorThrown);
		};

		// Make the request, allowing the user to override any Ajax options.
		var xhr = options.xhr = Backbone.ajax(_.extend(params, options));
		model.trigger('request', model, xhr, options);
		return xhr;
	};

	// Map from CRUD to HTTP for our default `Backbone.sync` implementation.
	var methodMap = {
		create: 'POST',
		update: 'PUT',
		patch: 'PATCH',
		delete: 'DELETE',
		read: 'GET'
	};

	// Set the default implementation of `Backbone.ajax` to proxy through to `$`.
	// Override this if you'd like to use a different library.
	Backbone.ajax = function() {
		return Backbone.$.ajax.apply(Backbone.$, arguments);
	};

	// Backbone.Router
	// ---------------

	// Routers map faux-URLs to actions, and fire events when routes are
	// matched. Creating a new one sets its `routes` hash, if not set statically.
	var Router = Backbone.Router = function(options) {
		options || (options = {});
		this.preinitialize.apply(this, arguments);
		if (options.routes) this.routes = options.routes;
		this._bindRoutes();
		this.initialize.apply(this, arguments);
	};

	// Cached regular expressions for matching named param parts and splatted
	// parts of route strings.
	var optionalParam = /\((.*?)\)/g;
	var namedParam    = /(\(\?)?:\w+/g;
	var splatParam    = /\*\w+/g;
	var escapeRegExp  = /[\-{}\[\]+?.,\\\^$|#\s]/g;

	// Set up all inheritable **Backbone.Router** properties and methods.
	_.extend(Router.prototype, Events, {

		// preinitialize is an empty function by default. You can override it with a function
		// or object.  preinitialize will run before any instantiation logic is run in the Router.
		preinitialize: function(){},

		// Initialize is an empty function by default. Override it with your own
		// initialization logic.
		initialize: function(){},

		// Manually bind a single named route to a callback. For example:
		//
		//     this.route('search/:query/p:num', 'search', function(query, num) {
		//       ...
		//     });
		//
		route: function(route, name, callback) {
			if (!_.isRegExp(route)) route = this._routeToRegExp(route);
			if (_.isFunction(name)) {
				callback = name;
				name = '';
			}
			if (!callback) callback = this[name];
			var router = this;
			Backbone.history.route(route, function(fragment) {
				var args = router._extractParameters(route, fragment);
				if (router.execute(callback, args, name) !== false) {
					router.trigger.apply(router, ['route:' + name].concat(args));
					router.trigger('route', name, args);
					Backbone.history.trigger('route', router, name, args);
				}
			});
			return this;
		},

		// Execute a route handler with the provided parameters.  This is an
		// excellent place to do pre-route setup or post-route cleanup.
		execute: function(callback, args, name) {
			if (callback) callback.apply(this, args);
		},

		// Simple proxy to `Backbone.history` to save a fragment into the history.
		navigate: function(fragment, options) {
			Backbone.history.navigate(fragment, options);
			return this;
		},

		// Bind all defined routes to `Backbone.history`. We have to reverse the
		// order of the routes here to support behavior where the most general
		// routes can be defined at the bottom of the route map.
		_bindRoutes: function() {
			if (!this.routes) return;
			this.routes = _.result(this, 'routes');
			var route, routes = _.keys(this.routes);
			while ((route = routes.pop()) != null) {
				this.route(route, this.routes[route]);
			}
		},

		// Convert a route string into a regular expression, suitable for matching
		// against the current location hash.
		_routeToRegExp: function(route) {
			route = route.replace(escapeRegExp, '\\$&')
				.replace(optionalParam, '(?:$1)?')
				.replace(namedParam, function(match, optional) {
					return optional ? match : '([^/?]+)';
				})
				.replace(splatParam, '([^?]*?)');
			return new RegExp('^' + route + '(?:\\?([\\s\\S]*))?$');
		},

		// Given a route, and a URL fragment that it matches, return the array of
		// extracted decoded parameters. Empty or unmatched parameters will be
		// treated as `null` to normalize cross-browser behavior.
		_extractParameters: function(route, fragment) {
			var params = route.exec(fragment).slice(1);
			return _.map(params, function(param, i) {
				// Don't decode the search params.
				if (i === params.length - 1) return param || null;
				return param ? decodeURIComponent(param) : null;
			});
		}

	});

	// Backbone.History
	// ----------------

	// Handles cross-browser history management, based on either
	// [pushState](http://diveintohtml5.info/history.html) and real URLs, or
	// [onhashchange](https://developer.mozilla.org/en-US/docs/DOM/window.onhashchange)
	// and URL fragments. If the browser supports neither (old IE, natch),
	// falls back to polling.
	var History = Backbone.History = function() {
		this.handlers = [];
		this.checkUrl = this.checkUrl.bind(this);

		// Ensure that `History` can be used outside of the browser.
		if (typeof window !== 'undefined') {
			this.location = window.location;
			this.history = window.history;
		}
	};

	// Cached regex for stripping a leading hash/slash and trailing space.
	var routeStripper = /^[#\/]|\s+$/g;

	// Cached regex for stripping leading and trailing slashes.
	var rootStripper = /^\/+|\/+$/g;

	// Cached regex for stripping urls of hash.
	var pathStripper = /#.*$/;

	// Has the history handling already been started?
	History.started = false;

	// Set up all inheritable **Backbone.History** properties and methods.
	_.extend(History.prototype, Events, {

		// The default interval to poll for hash changes, if necessary, is
		// twenty times a second.
		interval: 50,

		// Are we at the app root?
		atRoot: function() {
			var path = this.location.pathname.replace(/[^\/]$/, '$&/');
			return path === this.root && !this.getSearch();
		},

		// Does the pathname match the root?
		matchRoot: function() {
			var path = this.decodeFragment(this.location.pathname);
			var rootPath = path.slice(0, this.root.length - 1) + '/';
			return rootPath === this.root;
		},

		// Unicode characters in `location.pathname` are percent encoded so they're
		// decoded for comparison. `%25` should not be decoded since it may be part
		// of an encoded parameter.
		decodeFragment: function(fragment) {
			return decodeURI(fragment.replace(/%25/g, '%2525'));
		},

		// In IE6, the hash fragment and search params are incorrect if the
		// fragment contains `?`.
		getSearch: function() {
			var match = this.location.href.replace(/#.*/, '').match(/\?.+/);
			return match ? match[0] : '';
		},

		// Gets the true hash value. Cannot use location.hash directly due to bug
		// in Firefox where location.hash will always be decoded.
		getHash: function(window) {
			var match = (window || this).location.href.match(/#(.*)$/);
			return match ? match[1] : '';
		},

		// Get the pathname and search params, without the root.
		getPath: function() {
			var path = this.decodeFragment(
				this.location.pathname + this.getSearch()
			).slice(this.root.length - 1);
			return path.charAt(0) === '/' ? path.slice(1) : path;
		},

		// Get the cross-browser normalized URL fragment from the path or hash.
		getFragment: function(fragment) {
			if (fragment == null) {
				if (this._usePushState || !this._wantsHashChange) {
					fragment = this.getPath();
				} else {
					fragment = this.getHash();
				}
			}
			return fragment.replace(routeStripper, '');
		},

		// Start the hash change handling, returning `true` if the current URL matches
		// an existing route, and `false` otherwise.
		start: function(options) {
			if (History.started) throw new Error('Backbone.history has already been started');
			History.started = true;

			// Figure out the initial configuration. Do we need an iframe?
			// Is pushState desired ... is it available?
			this.options          = _.extend({root: '/'}, this.options, options);
			this.root             = this.options.root;
			this._wantsHashChange = this.options.hashChange !== false;
			this._hasHashChange   = 'onhashchange' in window && (document.documentMode === void 0 || document.documentMode > 7);
			this._useHashChange   = this._wantsHashChange && this._hasHashChange;
			this._wantsPushState  = !!this.options.pushState;
			this._hasPushState    = !!(this.history && this.history.pushState);
			this._usePushState    = this._wantsPushState && this._hasPushState;
			this.fragment         = this.getFragment();

			// Normalize root to always include a leading and trailing slash.
			this.root = ('/' + this.root + '/').replace(rootStripper, '/');

			// Transition from hashChange to pushState or vice versa if both are
			// requested.
			if (this._wantsHashChange && this._wantsPushState) {

				// If we've started off with a route from a `pushState`-enabled
				// browser, but we're currently in a browser that doesn't support it...
				if (!this._hasPushState && !this.atRoot()) {
					var rootPath = this.root.slice(0, -1) || '/';
					this.location.replace(rootPath + '#' + this.getPath());
					// Return immediately as browser will do redirect to new url
					return true;

					// Or if we've started out with a hash-based route, but we're currently
					// in a browser where it could be `pushState`-based instead...
				} else if (this._hasPushState && this.atRoot()) {
					this.navigate(this.getHash(), {replace: true});
				}

			}

			// Proxy an iframe to handle location events if the browser doesn't
			// support the `hashchange` event, HTML5 history, or the user wants
			// `hashChange` but not `pushState`.
			if (!this._hasHashChange && this._wantsHashChange && !this._usePushState) {
				this.iframe = document.createElement('iframe');
				this.iframe.src = 'javascript:0';
				this.iframe.style.display = 'none';
				this.iframe.tabIndex = -1;
				var body = document.body;
				// Using `appendChild` will throw on IE < 9 if the document is not ready.
				var iWindow = body.insertBefore(this.iframe, body.firstChild).contentWindow;
				iWindow.document.open();
				iWindow.document.close();
				iWindow.location.hash = '#' + this.fragment;
			}

			// Add a cross-platform `addEventListener` shim for older browsers.
			var addEventListener = window.addEventListener || function(eventName, listener) {
				return attachEvent('on' + eventName, listener);
			};

			// Depending on whether we're using pushState or hashes, and whether
			// 'onhashchange' is supported, determine how we check the URL state.
			if (this._usePushState) {
				addEventListener('popstate', this.checkUrl, false);
			} else if (this._useHashChange && !this.iframe) {
				addEventListener('hashchange', this.checkUrl, false);
			} else if (this._wantsHashChange) {
				this._checkUrlInterval = setInterval(this.checkUrl, this.interval);
			}

			if (!this.options.silent) return this.loadUrl();
		},

		// Disable Backbone.history, perhaps temporarily. Not useful in a real app,
		// but possibly useful for unit testing Routers.
		stop: function() {
			// Add a cross-platform `removeEventListener` shim for older browsers.
			var removeEventListener = window.removeEventListener || function(eventName, listener) {
				return detachEvent('on' + eventName, listener);
			};

			// Remove window listeners.
			if (this._usePushState) {
				removeEventListener('popstate', this.checkUrl, false);
			} else if (this._useHashChange && !this.iframe) {
				removeEventListener('hashchange', this.checkUrl, false);
			}

			// Clean up the iframe if necessary.
			if (this.iframe) {
				document.body.removeChild(this.iframe);
				this.iframe = null;
			}

			// Some environments will throw when clearing an undefined interval.
			if (this._checkUrlInterval) clearInterval(this._checkUrlInterval);
			History.started = false;
		},

		// Add a route to be tested when the fragment changes. Routes added later
		// may override previous routes.
		route: function(route, callback) {
			this.handlers.unshift({route: route, callback: callback});
		},

		// Checks the current URL to see if it has changed, and if it has,
		// calls `loadUrl`, normalizing across the hidden iframe.
		checkUrl: function(e) {
			var current = this.getFragment();

			// If the user pressed the back button, the iframe's hash will have
			// changed and we should use that for comparison.
			if (current === this.fragment && this.iframe) {
				current = this.getHash(this.iframe.contentWindow);
			}

			if (current === this.fragment) return false;
			if (this.iframe) this.navigate(current);
			this.loadUrl();
		},

		// Attempt to load the current URL fragment. If a route succeeds with a
		// match, returns `true`. If no defined routes matches the fragment,
		// returns `false`.
		loadUrl: function(fragment) {
			// If the root doesn't match, no routes can match either.
			if (!this.matchRoot()) return false;
			fragment = this.fragment = this.getFragment(fragment);
			return _.some(this.handlers, function(handler) {
				if (handler.route.test(fragment)) {
					handler.callback(fragment);
					return true;
				}
			});
		},

		// Save a fragment into the hash history, or replace the URL state if the
		// 'replace' option is passed. You are responsible for properly URL-encoding
		// the fragment in advance.
		//
		// The options object can contain `trigger: true` if you wish to have the
		// route callback be fired (not usually desirable), or `replace: true`, if
		// you wish to modify the current URL without adding an entry to the history.
		navigate: function(fragment, options) {
			if (!History.started) return false;
			if (!options || options === true) options = {trigger: !!options};

			// Normalize the fragment.
			fragment = this.getFragment(fragment || '');

			// Don't include a trailing slash on the root.
			var rootPath = this.root;
			if (fragment === '' || fragment.charAt(0) === '?') {
				rootPath = rootPath.slice(0, -1) || '/';
			}
			var url = rootPath + fragment;

			// Strip the fragment of the query and hash for matching.
			fragment = fragment.replace(pathStripper, '');

			// Decode for matching.
			var decodedFragment = this.decodeFragment(fragment);

			if (this.fragment === decodedFragment) return;
			this.fragment = decodedFragment;

			// If pushState is available, we use it to set the fragment as a real URL.
			if (this._usePushState) {
				this.history[options.replace ? 'replaceState' : 'pushState']({}, document.title, url);

				// If hash changes haven't been explicitly disabled, update the hash
				// fragment to store history.
			} else if (this._wantsHashChange) {
				this._updateHash(this.location, fragment, options.replace);
				if (this.iframe && fragment !== this.getHash(this.iframe.contentWindow)) {
					var iWindow = this.iframe.contentWindow;

					// Opening and closing the iframe tricks IE7 and earlier to push a
					// history entry on hash-tag change.  When replace is true, we don't
					// want this.
					if (!options.replace) {
						iWindow.document.open();
						iWindow.document.close();
					}

					this._updateHash(iWindow.location, fragment, options.replace);
				}

				// If you've told us that you explicitly don't want fallback hashchange-
				// based history, then `navigate` becomes a page refresh.
			} else {
				return this.location.assign(url);
			}
			if (options.trigger) return this.loadUrl(fragment);
		},

		// Update the hash location, either replacing the current entry, or adding
		// a new one to the browser history.
		_updateHash: function(location, fragment, replace) {
			if (replace) {
				var href = location.href.replace(/(javascript:|#).*$/, '');
				location.replace(href + '#' + fragment);
			} else {
				// Some browsers require that `hash` contains a leading #.
				location.hash = '#' + fragment;
			}
		}

	});

	// Create the default Backbone.history.
	Backbone.history = new History;

	// Helpers
	// -------

	// Helper function to correctly set up the prototype chain for subclasses.
	// Similar to `goog.inherits`, but uses a hash of prototype properties and
	// class properties to be extended.
	var extend = function(protoProps, staticProps) {
		var parent = this;
		var child;

		// The constructor function for the new subclass is either defined by you
		// (the "constructor" property in your `extend` definition), or defaulted
		// by us to simply call the parent constructor.
		if (protoProps && _.has(protoProps, 'constructor')) {
			child = protoProps.constructor;
		} else {
			child = function(){ return parent.apply(this, arguments); };
		}

		// Add static properties to the constructor function, if supplied.
		_.extend(child, parent, staticProps);

		// Set the prototype chain to inherit from `parent`, without calling
		// `parent`'s constructor function and add the prototype properties.
		child.prototype = _.create(parent.prototype, protoProps);
		child.prototype.constructor = child;

		// Set a convenience property in case the parent's prototype is needed
		// later.
		child.__super__ = parent.prototype;

		return child;
	};

	// Set up inheritance for the model, collection, router, view and history.
	Model.extend = Collection.extend = Router.extend = View.extend = History.extend = extend;

	// Throw an error when a URL is needed, and none is supplied.
	var urlError = function() {
		throw new Error('A "url" property or function must be specified');
	};

	// Wrap an optional error callback with a fallback error event.
	var wrapError = function(model, options) {
		var error = options.error;
		options.error = function(resp) {
			if (error) error.call(options.context, model, resp, options);
			model.trigger('error', model, resp, options);
		};
	};

	return Backbone;
});
